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WiNRADiO G305 Demodulators

G305 demodulators are DSP software plug-ins which fit into the G305 control panel. All the last IF (intermediate frequency stage) and the demodulation stage functions are performed in software. Having been freed from hardware constraints, this brings about unprecedented level of flexibility and performance to the receiver.

The G305 is being introduced with two demodulators, with others to follow. The Standard Demodulator is included as a standard part of the package, while the Professional Demodulator is optional.

The G305 Standard Demodulator provides excellent performance with minimum adjustable parameters, and facilities exceeding those of a demodulator of a conventional shortwave receiver in this price range (such as real-time spectrum scope).

The optional Professional Demodulator goes yet another step further and offers additional demodulation modes, and fully user-adjustable demodulation parameters, complete with interactive block diagrams of the internal structure of the demodulator, an additional dual real-time spectrum scope with vector voltmeter, SINAD and THD measurement, and many other facilities. This is a serious tool for a serious experimenter.

G305 Standard Demodulator

Standard Demodulator with Wide-FM option installed.

This demodulator is supplied as standard part of the G305 receiver package. It features AM, AMS (synchronous AM), AMN (narrow band AM), LSB, USB, FM6 (6 kHz FM), FMN (15 kHz FM) and CW modes, with fixed bandwidths (the FMW mode is optional). There is a real-time spectrum scope which shows the actual situation on the received band.

An interesting feature is Software AGC (i.e. digital AGC, in addition to the conventional analog AGC). The dual-loop AGC of the G305 receiver makes it possible to process the weakest as well as the strongest signals with equal clarity.

As the power of an ordinary PC does not yet allow to process the bandwidth of a wide-FM modulated signal (broadcast FM) directly, the option to receive wide-FM is offered separately. The Wide-FM Demodulator Option is based on conventional hardware (i.e. it is not software-defined) as an independent "receiver in a receiver". If this option is installed and selected, the real-time spectrum scope shows the demodulated signal audio spectrum instead of the radio frequency spectrum.

Clicking the Setup button, another window opens, making it possible to adjust the necessary minimum number of parameters for optimum performance:

The user adjustable parameters include the sound card selection, sampling rate (48000 samples/sec is recommended, 44100 can be also used), and the sound card input gain.

A clipping (input level overload) indicator and a CPU usage meter are also provided for the user's convenience.

With a minimum of initial set-up, the demodulator (and so the G305 receiver) are ready to go!

G305 Professional Demodulator

Professional Demodulator with Wide-FM option installed.

This advanced demodulator is offered as an optional extra. It adds DSB and ISB modes, additional Audio AGC settings and continuous IF bandwidth adjustment (from 100 Hz to 15 kHz). There are also user-definable IF bandwidth preset buttons at the bottom.

Many more exciting facilities are hidden under the Setup button: Optimized filter settings make it possible to increase the receiver sensitivity typically by 2 dB on AM, SSB and FM; and by up to 10 dB on CW.

The Professional Demodulator Setup window offers many additional facilities: In the section on the left, user-specified AGC constants and Secondary output have been added. The secondary output makes it possibleto pass the demodulated signal data directly to third-party signal processing applications, for example software decoders. For this, the WiNRADiO optional Digital Bridge™ Virtual Sound Card is useful to facilitate such seamless connection.

In the section on the right, the demodulator parameters (such as the digital filter lengths which directly influence the receiver's selectivity) can be adjusted by the user. There are separate "tabs" for independent setting of each of the eleven demodulation modes. There is also a facility to graphically adjust the desired passband of the audio filter, and a set of ten convenient user-definable IF bandwidth presets separate for each demodulation mode.

Clicking on the View Demodulator Structure button reveals an interactive diagram of the demodulator structure:

At the top, there is a block diagram showing the structure of the currently selected demodulator (each modulation mode has its own demodulator). Below, there are also two spectrum analyzers. Left clicking on any of the color points inside the block diagram will connect the left spectrum analyzer to the associated point (the color of the point will change to red). Right clicking will connect the right spectrum analyzer (the point color will turn blue).

At bottom left, there is a Vector Voltmeter showing amplitude and phase differences between the two selected points, at the cursor frequency.

There are also THD (total harmonic distortion) and SINAD (signal-plus-noise-plus-distortion to noise-plus-distortion) meters, to complement this unique instrument.

G305 Wide-FM Option

Professional Demodulator with Wide-FM option activated.

With the standard G305 receiver, the FMW mode button is disabled and the wide FM demodulation mode is not available. This is because wide FM demodulation is not possible to be provided as part of the G305 software-defined radio system, within the constraints imposed by the processing power of a standard personal computer.

However, wide-band FM demodulation capability is available as a factory-installed option. This is in fact a self-contained "hardware-defined" receiver which shares only the main receiver's front-endand first mixer, but has an independent wide-band analog processing circuit with a conventional "hardwired" demodulator.

If the Wide FM Option is installed, the FMW button becomes active. The demodulator spectrum display shows real-time spectrum of the demodulated audio. In the Professional Demodulator there is a user-definableaudio filter, displayed superimposed over the audio spectrum and graphically adjustable.

The G305 Professional Demodulator can be purchased later as a separate option, or bundled together with the G305 receiver, with a cost advantage. The model number of such bundled product is WR-G305i/PD (PCI version) or WR-G305e/PD (USB version). As a separate option, the Professional Demodulator can be purchased via our Direct Download server.

The G305 Wide-FM Option is factory-fitted and should be specified at the time of purchase. Retrofitting requires shipping the unit back to the factory and attracts additional cost. The model numbers of units fitted with the Wide-FM option are WR-G305i/WFM (PCI version) or WR-G305e/WFM (USB version).

The model numbers of receivers supplied with both the Professional Demodulator option and the Wide-FM option are WR-G305i/WFM/PD (PCI version) or WR-G305e/WFM/PD (USB version).